Microelectromechanical Systems (MEMS) resonators have been investigated for over forty years but have never delivered the high performance and low cost required of commercial oscillators. Packaging technology has been one of the primary limitations. MEMS resonators must be enclosed in very clean environments because even small amounts of surface contamination can significantly change resonator frequency. In addition, since the packaging can dominate the product cost and the applications are often cost sensitive, the packaging should be inexpensive. These requirements have now been met by SiTime’s MEMS First wafer-level encapsulation and packaging technology. SiTime builds encapsulated MEMS resonators in epitaxially sealed epipoly (epitaxially grown polysilicon) chambers buried under the wafer surface. The encapsulated resonator wafers are diced and molded into standard plastic IC packages with drive electronics. This encapsulation and packaging technology is inexpensive and extremely clean. The resulting silicon MEMS oscillators show performance levels similar to quartz and are expected to be suitable for a range of commercial applications.